Elephants can transmit signals through the ground over distances of several kilometers. New research has revealed what features of their ear structure and ear canals help them perceive these vibrations.
Elephant / © unsplash.com
Elephants are capable of sending messages to each other not only through airborne sounds but also by utilizing low-frequency vibrations that travel through the ground. A recent study has shed light on why these animals are so adept at detecting such signals.
This was reported by Earth.com.
In addition to their familiar trumpeting sounds and deep rumbles, elephants produce infrasonic signals that create ground vibrations. Other elephants can detect these seismic waves from several kilometers away. The vibrations travel through their feet and legs, reaching the skull and inner ear, effectively allowing the animals to “hear” with their entire bodies.
While scientists have long been aware of this elephant capability, the exact mechanism behind it remained inadequately understood. The latest research indicates that a significant role is played by their large middle ear and their ability to voluntarily close their ear canals.
Senior author of the study, Associate Professor of Otolaryngology at Harvard Medical School Sunil Puria, explained that in humans, closing the ear canal, for instance, while using earbuds, makes sounds produced by one’s own body—like footsteps or chewing—more noticeable. According to him, elephants employ this very principle to their advantage, enhancing their perception of ground-borne vibrations.
To test this hypothesis, researchers examined the temporal bones of deceased elephants and human donors, which house the middle and inner ears. Samples were subjected to vibrations mimicking sound transmission through the body, and laser measurements were used to determine how the middle ear ossicles responded to low and high frequencies. During the experiment, the ear canals were hermetically sealed with soft plugs.
The results revealed a substantial difference between humans and elephants. The elephants’ middle ear ossicles showed the strongest response at a frequency of approximately 400 Hz, whereas in humans, maximum sensitivity was observed around 1.2 kHz. Furthermore, at low frequencies, the stapes—one of the middle ear ossicles—moved three to four times more actively in elephants than in humans.
The researchers clarify that greater mobility on its own does not necessarily equate to superior hearing. However, it facilitates the transmission of more oscillations to the cochlea, the inner ear structure that converts mechanical vibrations into nerve signals for the brain.
The scientists also noted anatomical differences. Elephant middle ear bones are roughly nine times heavier than human ones, and their eardrums are seven times larger. According to the study’s authors, these dimensions are crucial for efficiently transmitting low-frequency sounds to the inner ear.
Additionally, the researchers hypothesize that elephants can voluntarily contract a muscle that closes the ear canal. They believe this action could significantly enhance bone conduction during the reception of infrasonic signals. The authors estimate that at the lowest frequencies, this feature could potentially improve elephants’ bone-conducted hearing by up to 30 times.
However, the scientists emphasize that the study has certain limitations. Due to the difficulties in obtaining and preparing tissue samples, the amount of material studied was small, and the preservation characteristics of the tissues might have influenced the results.
Earlier, scientists discovered that yawning might serve as a natural brain thermoregulation mechanism. This hypothesis was supported by experimental results involving cold compresses.
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